I wanted to take a moment to offer you an update on what we are doing to address the growing uselessness of hosted pop3/smtp as a means to communication over the Internet. The following is merely a status update, it does not offer an explicit date or implementation at which it may become available, only an indication that we are working on it. Support staff will not be able to give you an ETA.
Not a day goes by that we do not address at least a dozen support tickets with one ISP after another causing traffic interruption via port 25. Whether it is individual providers doing network policing and shaping intentionally, or they are being overloaded and experimenting new policies is inconclusive. What does appear to remain as a fact is that the remote SMTP access is rapidly becoming too unreliable for business use. The current recommendation is to rely on the SMTP server issued by your Internet Service Provider to relay mail.
Most providers outright proxy the port 25 connections through their networks. Bell South (AT&T) for example routes all port 25 traffic through their SMTP servers. Some Internet Service Providers are also enforcing SMTP auth on their users, making you authenticate against their SMTP servers. Some are silently dropping traffic on SMTP port 25. The problem becomes more impactful for mobile workers, mobile devices, etc.
We are working on providing alternate means for secure and reliable SMTP relay. All of the soon-to-be-proposed measures will require client reconfiguration. We hope that the additional services will further provide our client base with a reliable SMTP relay and ability to send/receive mail while roaming without depending on port 25. While we do offer SMTP via SSL, SMTP Auth, SMTP via ports 2525 and 25252 the documentation for those processes needs some work and we intend to provide it.
Note: Above only applies to our POP3/SMTP hosting service, not ExchangeDefender.